Simultaneous bilateral total knee arthroplasty lowers reoperation and cost at the expense of higher complications and mortality: a meta-analysis and systematic review.

BACKGROUND: The choice between simultaneous and staged bilateral total knee arthroplasty (TKA) remains controversial due to safety and resource considerations. This meta-analysis compared outcomes between the two approaches. METHODS: A total of 42 comparative studies published from 2001 to 2025 were included. A combined population of 567,915 patients was analyzed, with 225,181 undergoing simultaneous and 342,734 staged bilateral TKA. Random- or fixed-effects models were used to pool data across multiple clinical end points. Outcomes included in-hospital, first-year, and 1-2-year complications, mortality, functional outcomes, reoperations, persistent pain, and healthcare utilization metrics. Effect estimates were summarized using odds ratios (OR) for dichotomous outcomes and mean differences (MD) or standardized mean differences (SMD) for continuous outcomes, all with 95% confidence intervals (CI). RESULTS: Simultaneous TKA was associated with significantly higher odds of transfusion (OR 3.99; 95% CI 3.10-5.13; p < 0.001), first-year neurological complications (OR 1.48; 95% CI .128-1.71; p < 0.001), and first-year mortality (OR 2.43; 95% CI 2.02-2.92; p < 0.001). Pulmonary complications were significantly higher between 1 and 2 years postoperatively (OR 1.41; 95% CI 1.11-1.80; p = 0.005). However, joint infection (in-hospital, OR 0.59; 95% CI 0.40-0.89; p = 0.01), first-year periprosthetic fracture (OR 0.46; 95% CI 0.38-0.57; p < 0.001), and overall reoperation rates (OR 0.65; 95% CI 0.61-0.69; p < 0.001) were significantly lower in the simultaneous group. No significant differences were observed in functional scores, persistent pain, arthrofibrosis, knee instability, or extensor mechanism failure (p > 0.05). Simultaneous procedures were also associated with shorter operative times (MD -66.83 min; 95% CI -91.80 to -41.86; p < 0.001) and lower in-hospital costs (MD -$7062.67; 95% CI -13,927.78 to -197.56; p = 0.04). CONCLUSIONS: Simultaneous bilateral TKA offers advantages in operative efficiency, cost reduction, and lower reoperation and fracture rates, but carries increased odds of neurological complications, transfusion, and early mortality. Careful patient selection and perioperative management are essential to balance these trade-offs when considering simultaneous procedures.